1. Field of the Invention
The present invention relates to a mobile communication method, a base station, a radio terminal, and a low-power base station, which are used for a heterogeneous network.
2. Description of the Related Art
As a next-generation mobile communication system achieving communications with a higher-speed and larger-capacity, standardizations of LTE (Long Term Evolution) Advanced are in progress by the 3GPP (3rd Generation Partnership Project) which is a standardization organization thereof.
A network of the LTE Advanced under consideration for provision is a heterogeneous network in which a low-power base station with a small cell (a service area range) is effectively deployed in addition to a high-power base station (so-called, a macro base station). This low-power base station includes a so-called pico base station, femto base station, relay node, and the like.
In the heterogeneous network, a load of a high-power base station can be distributed to a low power base station, so that a service quality provided to a radio terminal can be improved. However, including cells with different sizes, the heterogeneous network necessitates a technology that can improve a service quality for a moving radio terminal (see, 3GPP contributed article, RP-110438, New work item proposal for Hetnet Mobility Improvements for LTE).